Method for use in making electronic devices having thin-film magnetic components

ABSTRACT

Disclosed herein is a method of forming electronic device having thin-film components by using trenches. One or more of thin-film components is formed by depositing a thin-film in the trench followed by processing the deposited thin-film to have the desired thickness.

CROSS-REFERENCE

The subject matter of US patent application US20070263434 to Dieny etal., published Nov. 15, 2007 is incorporated herein by reference in itsentirety.

TECHNICAL FIELD OF THE DISCLOSURE

The technical field of this disclosure relates to the art of methods formaking devices that comprise thin-film components; and moreparticularly, to the art of methods for use in making electronic deviceshaving thin-film magnetic components.

BACKGROUND OF THE DISCLOSURE

There are various types of electronic devices that comprise thin-filmmagnetic components, such as magnetic-random-access-memories andmagnetic recording heads. The thin-film magnetic components in thesedevices are often processed by standard photolithography and etchingtechniques during fabrication. For electronic devices having magneticthin-film components and stacks of other thin-film components ofdifferent natures or chemical properties, it becomes difficult toefficiently and successfully processing the thin-films using standardlithography and etching techniques. It becomes even more difficult touse standard photolithography and etching techniques to process thethin-films when the thin-films are to be defined into features withcharacteristic dimensions matching today's technology nodes, such as 130nm or less.

Taking magnetic-random-access memories (MRAM or MRAM cell) as anexample, MRAMs are a new non-volatile memory technology and have beendrown great attention in both scientific research laboratories andindustries. Their advantageous properties over existing memorytechnologies for storing digital signals have proved MRAMs to become apromising mainstream memory technology in the recent future.

A MRAM cell uses a magnetic tunnel junction (MTJ) as a storage element;and the MTJ comprises of two magnetic layers separated by a thin (suchas 1 nm) insulating layer. One of the two magnetic layers, which isreferred to as a reference layer, is characterized by fixedmagnetization. The other magnetic layer, which is referred to as astorage layer, is characterized by variable magnetization orientation.

The two magnetic layers of the MTJ are often based on 3d metals (such asFe, Co, Ni) and 3d metal alloys. The insulating layer laminated betweenthe two magnetic layers in the MTJ often comprises of alumina (Al₂O₃) ormagnesium oxide (MgO) although many other oxide/nitride materials couldin principle be used. In one example, one of the two magnetic layers ofthe MTJ is made of a synthetic antiferromagnet that involves ultra thinlayers of Co-alloys and ruthenium (Ru). One or both of the magneticlayers in the MTJ can be coupled with an anti-ferromagnetic layer, whichcan be a Mn alloy, such as FeMn, PtMn, and IrMn.

A MRAM cell may comprise additional functional elements, such as, bufferlayers to promote adhesion and texture, capping layers prevent corrosionor materials inter-diffusion, electrical contact layers, thermalbarriers, and spin polarizing layers. Because of different desiredfunctions of different elements, a MRAM cell may comprise of variousmaterials, some of which can be uncommon materials such as NiFe, CuN,NiFeCr, Pt, GeTeSb, and BiTe, as well as usual semiconductor materialssuch as Ti, TiN, TiW, TiWN, W, Ta, Cu, and CoSiN.

The combination of many materials with very different chemical naturesmakes it difficult if not impossible to etch using existingsemiconductor processing techniques, especially when it is to bepatterned into small individual elements (“cells”) at features sizesmatching today's technology nodes (130, 90, 65 nm going down to 45, 32,22 nm). In addition, it is always desired to preserve thechemical/crystalline nature of the tunnel barrier/storage and referencelayers interfaces so as to achieve desired electrical characteristics ofthe MRAM cell. In particular it is always desired to avoid disturbingthe magnetic properties of the reference and storage layers. It is alsodesired to avoid variation of the critical dimension of the MRAM cell.It is also desired to avoid damages of the tunnel barrier layer by meansof atomic diffusion of metallic species and/or modification of oxygencontent. It is further desired to avoid electrical shorting of thetunnel barrier layer by metallic sidewalls re-depositions duringfabrications.

Amongst the existing etch techniques that are commonly used in thesemiconductor and thin film industry, wet etch is unsuitable forprocessing MRAM features, especially those features with criticaldimensions. Ion beam etching (IBE) is unsuitable either for processingMRAM features due to the following reasons. An IBE etch is often drivenby high energy ions that sputter off the target material. Heavy sidewallre-deposition occurs as the sputter species being non-volatile bynature. Although etching at a grazing incidence may reduce sidewallre-deposition, such grazing incidence is primarily practical forisolated devices (such as recording heads) but not for dense MRAM cells,such as an array of MRAM cells, which is necessary for practical memoryapplications. Moreover, IBE etch may result in etched sidewalls beingslopped due to non-isotropic etch, which in turn, causes severe criticaldimension gain at the tunnel junctions of MRAM cells.

Reactive ion etching, which is capable of achieving features of criticaldimensions in MRAM cells and clean vertical sidewalls, is howeverdifficult to implement due to the multiple and often chemicallyincompatible elements in MTJs of MRAM cells. This arises from the factthat some of MTJs are comprised of highly non volatile elements (such asPt and Co). Some of MTJs are comprised of highly volatile elements (suchas Ge and Te); while some of MTJs are comprised of elements that arehighly sensitive to corrosion (such as elements Fe and Ni). Some MTJsare comprised of elements prone to solid state diffusion (such aselements Mn, Cu, and Sb). It is therefore very difficult to find anappropriate combination of chemistry and etching parameters (such astemperature and power) to achieve a proper etch.

MTJs of MRAM cells patterning is currently performed either by means ofIBE in the data storage market, where structures are isolated by natureand grazing incidences can be used, or by means of RIE in MRAMapplications, wherein large densities are required. It is believedhowever that as the feature size is decreased and the complexity of MTJstacks are increased, existing etching techniques will become more andmore difficult to implement in processing MRAM cells.

In view of the foregoing, it is desired for a method of processingthin-film components in electronic devices.

SUMMARY

In one example, a method is disclosed herein, the method comprising:providing a substrate that comprises a first magnetic layer on thesubstrate; forming a trench and a dielectric tunnel junction layer onthe substrate such that at least a portion of the exposed first portionof the trench is covered by the dielectric tunnel junction layer;depositing a second magnetic layer after the dielectric tunneling layersuch that a thin-film of the free magnetic layer is formed above thedielectric tunnel junction layer within the trench so as to form amagnetic tunnel junction at the first of the trench.

In another example, a method is disclosed herein, the method comprising:providing a substrate; forming a trench, comprising: depositing a trenchlayer on the substrate; and forming a trench in the trench layer;forming a plurality of thin-film components of a device in the trench,wherein the plurality of thin-film components comprises at least amagnetic thin-film component, comprising: depositing the plurality ofthin-film components in the trench and on the trench layer; andprocessing the deposited thin-film components by removing a portion ofthe deposited layers on the trench layer such that the thin-filmcomponents within the trench have a desired thickness.

In yet another example, a method is disclosed herein, the methodcomprising: providing a substrate comprising a first magnetic layer anda magnetic tunnel junction layer of a magnetic-random-access memorycell; depositing a trench layer on the substrate; etching the trenchlayer to form a trench, wherein the etching is stopped by the magnetictunnel junction layer or by a trench layer ; and wherein a portion ofthe tunnel junction layer is exposed at the first of the trench;depositing a stack of thin films in the trench and on the trench layer;and processing the deposited stack of thin films and the trench layersuch that the stack of thin films within the trench has a desiredthickness.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 a through FIG. 1 e diagrammatically illustrate cross-sectionalviews of an exemplary electronic devices having a magnetic thin-filmcomponent during an exemplary fabrication process;

FIG. 2 diagrammatically illustrates a cross-sectional view of anexemplary magnetic-random-access-memory magnetic stack;

FIG. 3 a through FIG. 3 c diagrammatically demonstrate an exemplarymethod of fabricating the magnetic-random-access-memory magnetic stackillustrated in FIG. 2;

FIG. 4 a through FIG. 4 d diagrammatically demonstrate another exemplarymethod of fabricating the magnetic-random-access-memory magnetic stackillustrated in FIG. 2;

FIG. 5 a through FIG. 5 d diagrammatically demonstrate yet anotherexemplary method of fabricating the magnetic-random-access-memorymagnetic stack illustrated in FIG. 2;

FIG. 6 a through FIG. 6 d diagrammatically illustrate cross-sectionalviews of an exemplary electronic devices having a magnetic thin-filmcomponent during another exemplary fabrication process;

FIG. 7 a and FIG. 7 b diagrammatically illustrate an exemplary method ofmaking electronic devices having magnetic films on a wafer-level.

DETAILED DESCRIPTION OF SELECTED EXAMPLES

Disclosed herein is a method for use in making electronic devices thatcomprise thin-film components. The method is particularly useful fordefining stacks of thin-films of different chemical properties ornatures in electronic devices, especially stacks of thin-film componentshaving magnetic thin-films in electronic devices. More particularly, themethod is of great value in defining stacks of thin-film componentshaving magnetic thin-film components with critical dimensions inelectronic devices.

The method uses a trench to define at least a thin-film component of anelectronic device, thereby, eliminating the necessity ofphotolithography and etching for defining the thin-film component. Thethin-film component can have a different chemical property or naturethan another or other components, especially thin-film component(s) ofthe electronic device. The thin-film component defined using the trenchcan be a member of a stack of thin-film components of an electronicdevice, or can be a stand-alone thin-film component of the electronicdevice; and may or may not be a magnetic thin-film component. By formingthe trench at desired dimension, the thin-film component fabricated byusing the trench may have any desired dimensions. In one example, thethin-film component may have a critical dimension, such as acharacteristic dimension (e.g. lateral or vertical dimension) of 2000 nmor less, 1500 nm or less, 700 nm or less. 400 nm or less, 200 nm orless, 100 nm or less, 90 nm or less, 65 nm or less, 45 nm or less, 32 nmor less, 22 nm or less.

A thin-film in this disclosure is referred to as a material layer thatis formed by depositing the material using one or more film depositiontechniques, such as physical-vapor-deposition (PVD),chemical-vapor-deposition (CVD),physical-energized-chemical-vapor-deposition (PECVD), and othertechniques. A magnetic thin-film in this disclosure is referred to as athin-film comprising at least a magnetic material. A thin-film componentin this disclosure is referred to as a functional component defined froma thin-film. A magnetic thin-film component in this disclosure isreferred to as a functional component of an electronic device derivedfrom a magnetic thin-film.

The method will be detailed in the following with reference to selectedexamples wherein the method is used for making electronic devices havingmagnetic thin-film components. It will be appreciated by those skilledin the art that the following discussion is for demonstration purposesand should not be interpreted as a limitation. Other variations with thescope of this disclosure are also applicable. For example, the method isalso applicable for making other types of electronic devices havingthin-film components.

Referring to the drawings, FIG. 1 a through FIG. 1 e diagrammaticallyillustrates an exemplary method of making an electronic device having amagnetic thin-film component by using a trench. As illustrated in FIG. 1a, the electronic device comprises substrate 100 and element 102 thatcomprises thin-film components 104, 106, and 108. The thin-filmcomponents each may comprise any desired materials; and the materials ofthe thin-film components may or may not have different chemicalproperties or natures. In one example, one or more of the thin-filmcomponents 104, 106, and 108 comprise a magnetic material. The magneticthin-film may be comprised of iron, nickel, cobalt, or rare earthelements, 3d metals (e.g. Fe, Co, Ni), 3d metal alloys (e.g. Mn alloysuch as FeMn, PtMn, and IrMn), Co-alloys (e.g. CoFeB and CoFe), NiFe,CuN, NiFeCr, Pt, GeTeSb, BiTe, as well as usual semiconductor materialssuch as Ti, TiN, TiW, TiWN, W, Ta, Cu, and CoSiN.

In another example, one or more of the thin-film components 104, 106,and 108 comprise a material such that a thin-film comprised of suchmaterial is difficult if not incapable to be patterned using standard orexisting photolithography techniques. In yet another example, one ormore of the thin-film components 104, 106, and 108 comprise a materialsuch that patterning/etching a thin-film comprised of such material isdifferent from that for other thin-film components of the electronicdevice.

In general, element 102 may be comprised any desired numbers ofthin-film components. Element 102 may also comprise other non-thin-filmcomponents (e.g. components not fabricated by standard thin-filmtechniques). The substrate (100) can be comprised of any suitablematerials. In one example, the substrate 100 can be comprised ofsubstantially a single material, such as a semiconductor material (e.g.Si or Ge), a dielectric material (e.g. SiO₂), or a conductive material(e.g. Al and Cu). The substrate (100) may be comprised of a crystallinematerial, an amorphous material, a glass, a polymer, a nanostructurematerial, or other types of materials. Alternatively, the substrate(100) may be a substrate assembly that comprises one or more functionalcomponents, such as thin-film components and other functionalcomponents, an example of which will be discussed afterwards withreference to FIG. 2.

Element 102 and the functional members in element 102 may have anydesired dimensions (e.g. lateral and vertical dimensions). In oneexample, element 102 and at least one of the thin-film components 104,106, and 108 of element 102 have a critical dimension; and the criticaldimension can be along the horizontal and/or vertical directions.

Element 102 on substrate 100 can be fabricated in many ways, one ofwhich is by using a trench, such as trench 110 in trench layer 112 asillustrated in FIG. 1 b. Referring to FIG. 1 b, trench layer 112 isdeposited on substrate 100. The trench layer may be comprised of anysuitable materials, such as a dielectric material (e.g. an oxide, anitride, a carbide, an oxy-nitride, a carbon-oxy-nitride, or anycombinations thereof) or a wide range of other materials. In oneexample, the trench layer may be comprised of amorphous silicon or othersuitable materials, such as organic materials and polymers.

Depending upon the specific material, the trench layer (112) can bedeposited using any standard or existing film-deposition techniques,such as CVD, PVD, or PECVD. The deposited trench layer (112) ispatterned, for example using an existing photolithography technique, soas to form trench 110. The deposited trench layer is patterned, forexample, using a suitable photolithographic technique.

As an alternative feature, a protection layer, such as protection layer113 can be deposited on substrate 100 before depositing trench layer112. The protection layer (113) can be used for protecting the topsurface of the substrate, especially the portion of the top surface atthe bottom of the desired trench, during the processes of depositing thetrench layer and patterning the trench layer for forming the trench. Theprotection layer (113) can be removed before releasing the electronicdevice. Specifically, the bottom portion of the protection layer can beremoved during or after forming the trench, and preferably beforedepositing the thin-films in the trench, such as before depositing athin-film for forming thin-film component 104 in the trench. Theremaining portion of the protection layer (113) can be removed beforereleasing the electronic device, such as before, during, or after theetching process for removing the trench layer 112. In some examples, theprotection layer (113) can also be used as an etch stop layer.Specifically, the protection layer (113) can be comprised of a materialthat is highly resist to the etching used for patterning the trenchlayer (112) in forming trench 110. For example, the protection layer canbe comprised of carbon, which acts simultaneously as an etch stop layer.

Trench 110 has a dimension corresponding to the dimension of the desiredelement (e.g. element 102) to be formed using the trench. For example,trench 110 has a depth that is substantially equal to the desiredthickness of the element to be formed using the trench. In the exampleof forming element 102 using the trench, trench 110 has a depth that issubstantially equal to the total thicknesses of thin-film components104, 106, and 108 of element 102. The desired depth of the trench can beobtained by depositing the trench layer (113) at a proper thickness. Thelateral dimension (e.g. width D) of trench 110 corresponds to thelateral dimension of the element to be formed using the trench. In anexample wherein element 102 has a critical lateral dimension, trench 110has a characteristic lateral dimension that is substantially equal tothe desired critical lateral dimension of element 102.

The side walls of trench 110 may be substantially vertical such thatangle θ is substantially 90°. In other examples, the trench has slopedsidewalls such that angle θ is off from 90°. Specifically, angle θ canbe less than 90°, such as 30° or less, 20° or less, 10° or less, 5° orless but larger than 0°. This configuration is advantages for improvingcontinuity of the thin-film(s), especially the continuity of themagnetic property of the magnetic thin-film, subsequently deposited inthe trench, which will be discussed afterwards with reference to FIG. 2.

In another example, the angle θ can be larger than 90°, such as 110° orlarger, 120° or larger, 140° or larger, 160° or larger but less than180°. This configuration is especially useful for obtainingdiscontinuity of the portion of the subsequently deposited thin-film(e.g. a thin-film for defining thin-film component 104) in the trenchfrom the top surface of the protection layer (if provided) or the topsurface of the substrate 100 if the trench is formed on the surface ofthe substrate.

The trench can be formed into any desired geometric shapes. In the topview, the trench can be a rectangle, square, circle, or other simpleshapes. The trench can alternatively be formed to take other complicateshapes, such as an “L” shape, as diagrammatically illustrated in FIG. 1c, and other desired shapes.

Thin-film components can then be formed by using the trench asdiagrammatically illustrated in FIG. 1 d. Referring to FIG. 1 d, thinfilms 104, 106, and 108 can be deposited consecutively on the patternedtrench layer 112 and the substrate 100 with each having a desiredthickness. The portions of the deposited thin-films 104, 106, and 108above the top surface of the trench layer 112 can be removed whileleaving portions of the thin-films 104, 106, and 108 in the trench 110,as diagrammatically illustrated in FIG. 1 e. The portions of thethin-films above the trench layer 112 can be removed by many possibleways, such as chemical-mechanical-polishing (CMP). The remainingportions of the thin-films in the trench 110 form the desired element102.

Because the thin film components (e.g. components 108, 16, and 104) areformed with the trench (110) and thin-film deposition techniques, one ormore formed thin film components, such as thin-film components 104 and106, have vertically extended end portions due to the trench. As aconsequence, for example, thin film components 104 and 106 each have a“U” shape. Because of the CMP followed by thin film deposition, thetopmost thin-film component (e.g. 108) can be wrapped up by thevertically extended end portions of the lower thin-film component(s).

Because the trench has the desired shape with desired dimensions, theelement 102 formed in the trench has the desired shape and dimensions.As such, the thin-film components 104, 106, and 108 of element 102 areformed from thin-films but without lithography.

After forming the thin-film components, the trench layer 112 can beremoved by suitable methods, such as etching, depending upon thematerial of the trench layer. In examples wherein the trench layer is tobe removed by etching, energized or non-energized or combinationsthereof can be used. The etching can be wet etching or dry etching or acombination thereof. Depending upon the material of the trench layer, awide range of etchant can be used, such as etchants comprising aspontaneous chemical component that is capable of chemically reacts withthe target trench material spontaneously.

The above method can be used in fabricating a wide range of deviceshaving thin-film components. As an example, the above method can be usedin fabricating magnetic-random-access memories (MRAM), one of which isdiagrammatically illustrated in FIG. 2. It will be appreciated by thoseskilled in the art that the MRAM cell to be discussed in the followingis only one of many possible MRAM cells that can be fabricated byexamples of the method as discussed above with reference to FIG. 1 athrough FIG. 1 e. For example, the method can be implemented infabrications of other varieties of MRAMs, such as field-induced-magneticswitching devices, thermally-assisted magnetic switching devices,current-induced magnetic switching devices, and other devices withthin-film components that may or may not be magnetic.

Referring to FIG. 2, the exemplary MRAM comprises of first portion 101,second portion 103, and dielectric tunnel-junction layer 122. The firstportion 101 comprises fixed magnetic layer 120 whose magneticorientation does not change during operation. The second portion (103)comprises free-magnetic layer 124 whose magnetic orientation variesduring operation. It is noted that even though it is shown in FIG. 2that the free magnetic layer is above the fixed magnetic layer, it isonly one of examples. In other examples, the fixed magnetic layer can beabove the free magnetic layer. Varieties of other functional elementscan be included in the second and first portions. For example, the firstportion (101) may also comprise electrode 114, thermal barrier 116, andbuffer layer 118. The second portion (102) may also comprise barrierlayer 126 and electrode 128.

The electrode layers 128 and 114 provide electrical contacts(electrodes). Accordingly, the electrode layers each comprise anelectrically conductive material, such as metallic elements, metallicalloys, metallic compounds, inter-metallic compounds, and anycombinations thereof. Each electrode layer can be a laminate comprisingmultiple layers of different materials.

The thermal barrier layers (126 and 116) act to prevent thermal leakageto/from the magnetic element. Specifically, the thermal layers are usedfor confining heat at the level of the storage layer so as to minimizethe power consumption during operation (e.g. during switching of themagnetization orientation). In one example, the thermal barrier layerhas a thermal conductivity of 2 W/m.k or lower, such as 1 W/m.k orlower, or 0.5 W/m.k or lower, and preferably has a heating or coolingtime of 10 ns or less, such as 5 ns. An exemplary structure of thethermal layers (126 and 116) is diagrammatically illustrated in FIG. 6,which will be detailed afterwards.

The MRAM as illustrated in FIG. 2 can be fabricated by using a trench asdiscussed above with reference to FIG. 1 a through FIG. 1 e. One exampleis diagrammatically illustrated in FIG. 3 a through FIG. 3 c.

Referring to FIG. 3 a, portion 101 is provided, which comprises fixedmagnetic layer 120. The portion 101 can be fabricated by a sequence ofstandard thin-film techniques to form desired thin-film components, suchas thermal barrier layer 118 and fixed magnetic layer 120, of portion101. The portion 101 is then treated as substrate 100 in FIG. 1 athrough FIG. 1 e; and the other thin-film components of the MRAM areconsecutively formed on the substrate. As illustrated in FIG. 3 a,dielectric tunnel junction layer 122 is formed on substrate 101, by forexample, a standard thin-film deposition technique, which may befollowed by patterning if needed.

As illustrated in FIG. 3 b, trench layer 132 can be deposited on thedielectric tunnel junction layer 122. The deposited trench layer has athickness that is substantially equal to the desired thickness of theelement to be formed in the trench (e.g. the total thickness ofthin-film components 124 and 126). As an alternative feature, throughnot required, protection layer 130 can be deposited prior to trenchlayer 132 for protecting the dielectric tunnel junction layer (122). Thetrench layer (132) and protection layer 130 (if provided) can bepatterned so as to form trench 134 as illustrated in FIG. 3 c. Thefunctional thin film components, such as free magnetic layer 124,barrier layer 126, as well as electrode 128, of portion 103 asillustrated in FIG. 2 can then be formed in trench 134 using the methodas discussed above with reference to FIG. 1 a through FIG. 1 e, whichwill not be repeated herein. After forming the functional members of theMRAM, the trench layer (132) may or may not be removed.

During the process for forming trench 134 s shown in FIG. 3 c, thetrench material at the trench location may or may not be removed afteropening the trench at the desired trench location. For example, if thetrench material left in trench 134 is a thin enough insulation layer andcan be a part of the tunnel junction layer, this trench material can bemaintained as part of the tunnel junction layer. Otherwise, the trenchmaterial at the location of desired trench 134 is removed. For examplewherein the trench layer is comprised of amorphous C, an oxygen ashprocess can be performed to remove the trench material at desired trenchlocation 134.

It is noted that the trench (134 as shown in FIG. 3 c) has an angle θ,which can be configured into any desired values. As discussed above withreference to FIG. 1 b, the trench (110) may have tilted side walls; andangle θ can be less than 90°, such as 30° or less, 20° or less, 10° orless, 5° or less but larger than 0°; or alternatively, can be largerthan 90°, such as 110° or larger, 120° or larger, 140° or larger, 160°or larger but less than 180°. In examples wherein angle θ is less than90° but larger than zero degree, the portion of the deposited freemagnetic layer (124) in the trench can be substantially continuous fromthe portion of the tunnel junction layer 122 without disturbing itsmagnetic property.

When θ is small, the magnetostatic field generated by the magneticlayers (i.e. the free magnetic layer 124 and the fixed magnetic layer120) remains marginal to enable the switching fields of the magneticlayer (e.g. the free magnetic layer 124) can remain comparable to thatof blanket planar thin-films.

In examples wherein angle θ>90°, the portion of the deposited freemagnetic layer (124) in the trench can be discontinuous from the portionof the tunnel junction layer 122. To improve the discontinuity, theangle θ can be large enough such that the thin-film (e.g. the freemagnetic layer 124) at the bottom of the trench can be sufficientlyflat.

Another exemplary method of forming the MRAM illustrated in FIG. 2 isschematically demonstrated in FIG. 4 a through FIG. 4 d. Referring toFIG. 4 a, the first portion 101 comprising fixed magnetic layer 120 isprovided, which can be prepared by the same method as discussed abovewith reference to FIG. 3 a. Trench layer 132 is deposited on substrate101 and patterned so as to form trench 136 as illustrated in FIG. 4 b.The trench layer has a thickness that is substantially equal to thethickness of the desired thin-film components to be formed in thetrench. Dielectric tunnel junction layer 122 and the functional elements(e.g. free magnetic layer 124 and thermal barrier layer 126) of theportion 103 of MRAM (as shown in FIG. 2) are consecutively deposited intrench 136, as illustrated in FIG. 4 c. A polishing process, such as achemical-mechanical-polishing process, can be performed to remove theportions of the deposited thin-films above the surface of trench layer132 as illustrated in FIG. 4 d. Other fabrication process can beperformed. For example, an electrode can be formed on the top surface ofthermal barrier layer 126.

Yet another exemplary method of making the MRAM illustrated in FIG. 2 isdiagrammatically illustrated in FIG. 5 a through FIG. 5 d. Referring toFIG. 5 a, the first portion (101) comprising fixed magnetic layer 120 isprovided, which can be prepared by the same method as discussed abovewith reference to FIG. 3 a.

Trench layer 132 is deposited on substrate 101 followed by patterning soas to form trench 138 as illustrated in FIG. 5 b. In this example, thetrench (138) has a depth less than the total thickness of the thin-filmcomponents of the second portion 103 of MRAM in FIG. 2. However, thetrench (138) has a lateral dimension corresponds to the desired lateraldimension of the tunnel junction. Specifically, the bottom of the trenchcan have a critical dimension (or other desired dimensions of themagnetic tunnel junction) corresponding to the dimension of the magnetictunnel junction.

Dielectric tunnel junction layer 122, free magnetic layer 124, andthermal barrier layer 126 can be formed in the trench and on the topsurface of the trench layer (132) as shown in FIG. 5 c. The thermalbarrier layer (126), or both of the thermal barrier layer 126 and thefree magnetic layer 124, or all of the three layers 122, 124, and 126can be patterned to obtain the portion 103 of the MRAM with the desireddimension, as illustrated in FIG. 5 d.

In addition to forming the portion 103 of the MRAM in FIG. 2 by using atrench as discussed above, the first portion 101 of the MRAM can also beformed by using a trench, an example of which is diagrammaticallyillustrated in FIG. 6 a through FIG. 6 d. Referring to FIG. 6 a, trench166 is formed in trench layer 164 that is deposited on substrate 162. Inan alternative example, a trench (e.g. trench 166) can be directlyformed in a trench substrate 168 as diagrammatically illustrated in FIG.6 b. The trench substrate can be comprised of a material for the trenchlayer 112 as discussed above with reference to FIG. 1 a through FIG. 1e. The trench can be formed in the trench substrate 160 by many possibleways, such as photolithography followed by etching.

The thin film components (e.g. electrode 114, thermal barrier 116,buffer layer 118 (if provided), and the fixed magnetic layer 120) offirst portion 101 of the MRAM as shown in FIG. 2 can be consecutivelydeposited on the trench layer 164 and in the trench 166 followed by CMPor other possible methods (e.g. etching) as diagrammatically illustratedin FIG. 6 c. Because the tunnel junction layer 122 often has a thicknessaround 1 nanometer or less, the tunnel junction layer 122 is preferablydeposited on the top surface of fixed magnetic layer 120 by a thin-filmdeposition technique or other possible techniques, such as epitaxialgrowth. Alternatively, the tunnel junction layer 122 can be formed byusing the trench and the CMP (or other possible techniques) technique asother thin-film components of the first portion 101.

Thin-film components of the second portion 103 of the MRAM in FIG. 2 canbe formed on the fabricated first portion 101 by using another trench asdiagrammatically illustrated in FIG. 6 d. Referring to FIG. 6 d, atrench can be formed in trench layer 170 that is deposited on thefabricated first portion 101 and the trench layer 164. Thin-filmcomponents of the free magnetic layer 124 and the thermal barrier layer126 can be consecutively formed in the trench and on the trench layer170 by using any one of the methods as discussed above with reference toFIG. 3 a through FIG. 5 d, which will not be repeated herein.

The method implemented for fabricating MRAM cells as discussed above hasmany advantageous over existing techniques. For example, the lateralcritical dimension of a MRAM cell is defined by a trench instead ofetching processes as used in current technologies. Specifically, themethod avoids, e.g. top magnetic etch (element 100 in FIG. 6 c) withcomplex hard mask or reactive ion etching processes, which are used incurrent MRAM technologies. The method avoids tunnel barrier shorts thatare the most detrimental factor in current etching-based techniques forfabricating MRAMs. By reducing the characteristic dimension of thetrench, features of smaller critical dimensions in MRAM cells can beobtained without reducing the performance or properties of MRAM cells.The planarized (e.g. CMP) surface can be subsequently processed foradditional features, such as metal lines and contact via using standardprocess. The planarized CMP surface ensures electric contact openings,which in turn, avoids top contact via to connect the MRAM cell. Themethod can be substantially fully scalable with substantially nomodification for defining features of MRAM cells with reduced criticaldimensions. The MRAM cells fabricated thereof may have improved thermalstability (e.g. when the storage layer implemented as bottom magnet) andimproved scalability as compared to similar MRAM cells but arefabricated using existing techniques. The MRAM cells fabricated thereofmay also have improved temperature window (e.g. when reference layerimplemented as bottom magnet with large AR and anit-ferromagneticbiaising layer replaced by SAF) as compared to similar MRAM cells butare fabricated using existing techniques. As a result, higher yields andlower costs of MRAM cells, especially MRAM cell arrays are expected.

It will be appreciated by those skilled in the art that the abovemethods using a trench are discussed with reference to particularexamples of MRAM. In fact, the methods can be implemented to formvarious MRAM devices or other devices having thin-film components.

Anyone of the methods of making one or more thin-film components of adevice as disclosed above can be implemented to fabricate MRAM and othertypes of electronic devices on a wafer level as diagrammaticallyillustrated in FIG. 7 a and FIG. 7 b. Referring to FIG. 7 a, substrate194 comprising a plurality of die areas (e.g. die area 196) is provided.MRAMs (or other electronic devices) are formed in the die areas. In oneexample, an array of MRAMs is formed in each die area asdiagrammatically illustrated in FIG. 7 b. Referring to FIG. 7 b, thearray of MRAMs comprises M×N MRAMs (e.g. MRAM 198). M and N can be anydesired integer numbers; and the product of M and N is referred to asthe capacity of the non-volatile storage of the MRAM array.

The MRAMs can be formed in each die area by using the method asdiscussed above of this disclosure. After forming the MRAM arrays in thedie areas, the die areas can be singulated from the wafer so as toobtain individual MRAM chips.

It will be appreciated by those of skill in the art that a new anduseful method for forming electronic devices by using trenches have beendescribed herein. In view of the many possible embodiments, however, itshould be recognized that the embodiments described herein with respectto the drawing figures are meant to be illustrative only and should notbe taken as limiting the scope of what is claimed. Those of skill in theart will recognize that the illustrated embodiments can be modified inarrangement and detail. Therefore, the devices and methods as describedherein contemplate all such embodiments as may come within the scope ofthe following claims and equivalents thereof.

1. A method, comprising: providing a substrate that comprises a firstmagnetic layer on the substrate; forming a trench and a dielectrictunnel junction layer on the substrate such that at least a portion ofthe exposed bottom portion of the trench is covered by the dielectrictunnel junction layer; depositing a second magnetic layer after thedielectric tunneling layer such that a thin-film of the second magneticlayer is formed above the dielectric tunnel junction layer within thetrench so as to form a magnetic tunnel junction at the bottom of thetrench.
 2. The method of claim 1, wherein the step of forming a trenchcomprises: depositing a trench layer on the substrate; and patterningthe trench layer so as to form the trench.
 3. The method of claim 2,further comprising: removing the deposited free magnetic layer from thesurface of the trench layer such that the free magnetic layer within thetrench has top surface that is substantially within the top surface ofthe trench layer.
 4. The method of claim 2, further comprising:depositing a thermal barrier layer or a plurality of thin-film layers onthe free magnetic layer; and removing a portion of the deposited thermalbarrier layer or a portion of the plurality of thin-film layers from thesurface of the trench layer such that the thermal barrier layer or theplurality of thin-film layers within the trench has top surface that issubstantially larger than the top surface of the trench layer.
 5. Themethod of claim 1, wherein the step of forming a dielectric tunneljunction layer and a trench layer comprises: forming the dielectrictunnel junction layer on the surface of the first magnetic layer of thesubstrate; depositing the trench layer on the dielectric tunnel junctionlayer; and patterning the trench layer so as to form the trench.
 6. Themethod of claim 1, wherein the step of forming a dielectric tunneljunction layer and a trench layer comprises: depositing the trench layeron the surface of the fixed magnetic layer of the substrate; patterningthe trench layer so as to form the trench such that a portion of thefixed magnetic layer is exposed at the bottom of the trench; anddepositing the dielectric tunnel junction layer such that the dielectrictunnel junction layer covers at least the bottom portion of the trench.7. The method of claim 1, further comprising: depositing anotherthin-film on the free magnetic layer; and patterning said anotherthin-film according to a characteristic dimension of the trench.
 8. Themethod of claim 7, wherein said another thin-film is a thermal barrierlayer.
 9. A method, comprising: providing a substrate; forming a trench,comprising: depositing a trench layer on the substrate; and forming atrench in the trench layer; forming a plurality of thin-film componentsof a device in the trench, wherein the plurality of thin-film componentscomprises at least a magnetic thin-film component, comprising:depositing the plurality of thin-film components in the trench and onthe trench layer; and processing the deposited thin-film components byremoving a portion of the deposited layers on the trench layer such thatthe thin-film components within the trench have a desired thickness. 10.The method of claim 9, wherein the step of processing the depositedthin-film components comprises; polishing the position on the trenchlayer by a chemical-mechanical polishing technique.
 11. The method ofclaim 9, wherein the device is a magnetic-random-access memory cell thatcomprises a magnetic-tunnel-junction that comprises a tunnel junctionlayer positioned between a free magnetic layer and a fixed magneticlayer.
 12. The method of claim 11, wherein the substrate comprises thefixed magnetic layer and the tunnel junction layer; and wherein thetrench layer is comprised of a dielectric material; and wherein thestack of thin-film components within the trench comprises the freemagnetic layer.
 13. The method of claim 12, wherein the stack ofthin-film components in the trench has a lateral characteristicdimension of 100 nanometers or less.
 14. The method of claim 12, whereinthe stack of thin-film components in the trench has a lateralcharacteristic dimension of 45 nanometers or less.
 15. The method ofclaim 12, wherein the stack of thin-film components further comprises athermal barrier for preventing thermal leakage from the free magneticlayer.
 16. The method of claim 11, wherein the magnetic tunnel junctionis substantially within the trench.
 17. The method of claim 16, whereinthe step of providing the substrate comprises: providing a sacrificialsubstrate; forming another trench, comprising; depositing another trenchlayer on said sacrificial substrate; and forming another trench in saidanother trench layer; forming a plurality of thin-film components of thedevice in the trench, comprising; depositing a plurality of thin filmsin the trench and on the sacrificial substrate; and removing at least aportion of the deposited thin-film components and said another trenchlayer such that the thin-film components within said another trench hasa desired thickness.
 18. The method of claim 11, wherein the substratecomprises the free magnetic layer and the tunnel junction layer; andwherein the trench layer is comprised of a dielectric material; andwherein the stack of thin-film components within the trench comprisesthe fixed magnetic layer.
 19. A method, comprising: providing asubstrate comprising a first magnetic layer and a magnetic tunneljunction layer of a magnetic-random-access memory cell; depositing atrench layer on the substrate; etching the trench layer to form atrench, wherein the etching is stopped by the magnetic tunnel junctionlayer; and wherein a portion of the tunnel junction layer is exposed atthe bottom of the trench; depositing a stack of thin films in the trenchand on the trench layer; and processing the deposited stack of thinfilms and the trench layer such that the stack of thin films within thetrench has a desired thickness.
 20. The method of claim 19, wherein thestep of processing the deposited stack of thin films comprises:processing the deposited stack of thin films and the trench layer usinga chemical-mechanical-polishing technique.
 21. The method of claim 10,wherein the stack of thin films within the trench comprises a secondmagnetic layer.
 22. The method of claim 21, wherein the second magneticlayer is a free magnetic layer; and the first magnetic layer is a fixedmagnetic layer.
 23. The method of claim 19, herein the stack ofthin-film components in the trench has a lateral characteristicdimension of 100 nanometers or less.
 24. The method of claim 19, whereinthe stack of thin-film components further comprises a thermal barrierfor preventing thermal leakage from the free magnetic layer.
 25. Themethod of claim 19, wherein the step of providing the substratecomprises: providing a sacrificial substrate; forming another trench,comprising; depositing another trench layer on said sacrificialsubstrate; and forming another trench in said another trench layer;forming a plurality of thin-film components of the device in the trench,comprising; depositing a plurality of thin films in the trench and onthe sacrificial substrate; and removing at least a portion of thedeposited thin-film components and said another trench layer such thatthe thin-film components within said another trench has a desiredthickness.